The long-term objectives are improved treatment results in patients with hemifacial microsomia, and the application of successful treatment procedures to other types of craniofacial anomalies (i.e. syndromes involving cranial and midface malformations). At the present time, any desired increase in length of an underdeveloped mandible can be achieved with long- term stable results. It is also possible to achieve growth by bone apposition of a lengthened structure. At this time we are less successful in applying pertinent biological principles to advance midline and lateral structures in the midface or to achieve a normal shape of a constructed mandibular ramus when mandibular muscles are severely hypotrophic or missing. It has not yet been clarified which muscles or which properties of muscles are essential for the development of the various parts of craniofacial bones. This proposal has three specific aims: 1. Determine changes in size, volume and neuromuscular properties of congenitally underdeveloped muscles in response to altered skeletal morphology. 2. Determine if recruitment patterns for mastication differ from the normal in; 1) subjects with missing joint structures, but presence of a condylar process and lateral pterygoid muscles (Type I) and in 2) subjects with absence of the condylar process and probably absence of the lateral ptergoid muscles (Types IV and V). 3. a) Determine if the functional asymmetries which are present in the nasopharyngeal area in HFM are the result of structural asymmetries or have a neuromuscular basis, b) study compensation mechanisms for achieving velopharyngeal closure. Electromyographic data obtained by surface electrodes from jaw elevator muscles during rest, voluntary jaw movements, and during mastication will be assessed before and during stages of treatment. CT scan techniques will be utilized to assess muscle volume, cross-sectional area and length before and after mandibular repositioning. In order to assess structural asymmetries in the nasopharyngeal area CT and radiographs will be utilized. For assessment of neuromuscular asymmetries clinical examination and endoscopic examination with fiber- optic instrumentation will be used. In order to assess velopharyngeal function speech samples will be analyzed and orovelopharyngeal coordination pattern test utilized. Further understanding of the association between the neuromuscular system and the skeletal components should result from this research.